Movement in and out of cells Learning Objectives

Movement in and out of cells Learning Objectives - to know that dissolved substances can move in and out of cells by diffusion. - to know that particles move from a high concentration to a low concentration. - to know that the greater the difference in concentration the faster the rate of diffusion

Movement Dissolved substances can move in and out of cells by diffusion, osmosis and active transport. Diffusion and osmosis are passive and require no energy. Active transport is active and requires energy.

Diffusion in action: one gas

Diffusion in action: two gases

Changing concentrations During diffusion molecules move from an area of high concentration to an area of low concentration. They are said to move down a concentration gradient. Diffusion is a passive process which means that no energy is needed. high concentration low concentration Molecules diffuse until they are evenly spaced apart and equilibrium is reached.

What happens in the alveoli?

Diffusion across the alveoli • The gases move from a high concentration to a low concentration. • So oxygen moves from inside the alveoli to the blood where it binds to haemoglobin. • Carbon dioxide is present in high concentration so moves into the alveoli and is breathed out. • The greater the difference in concentration the faster the rate of diffusion.

Diffusion and the placenta How does the placenta work? umbilical cord umbilical artery umbilical vein blood to mother low in O 2/nutrients, high in CO 2/waste placental villi increase surface area for diffusion blood from mother high in O 2/nutrients, low in CO 2/waste